Vacuum tube



Get 2% 1925.

H. E. METCALF VACUUM TUBE Filed March 23, 1925 [hue/"liar:

Patented Oct. 20, 1925.

UNITED STATES PATENT OFFICE.

HERBERT E. ME'I'CALF, OF SAN LEANDRO, CALIFORNIA, ASSIGNOR TO THE MAGNAVOX COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF ARIZONA.

VACUUM TUBE.

Application filed March 23, 1925. Serial No. 17,575.

To all whom it may concern:

Be it known that I, I'IERBERT Ill. Mnrronnr, a citizen of the United States, residing at San Leandro, county of Alameda, and State of California, have invented new and use- :tul Improvements in Vacuum Tubes, of which the following is a specification.

This invention relates to vacuum tubes, particularly of the three electrode type for use as rectifiers, amplifiers and electric wave generators. The object of the invention is to improve the mechanical construction and operation of such a device, whereby the control electrode may be made out of metallic stampings and still maintain its sensitivity to use oscillation.

A further object of the invention is to improve the construction of such a device from the manufacturing point of View, whereby the filament does not have to be assembled in the interior of a closed cylinder, so that great speed of assembly may be obtained and yet the results will be identical of the common type of grid tube. In addition, the internal capacity of the device is kept to a minimum, especially the capacity between grid and plate. This lower internal capacity is uite necessary when tubes are used in mo ern radio frequency circuits.

A still further object of the invention is to provide a control electrode which is extremely rugged in character and which can be stamped by automatic machinery so that every one of them is identical. Such a construction makes for extreme uniformity of tubes in commercial production.

In the construction of three-electrode tubes, the practice has been quite common to employ a grid between the plate and filament. This usually consists of one or two supporting members on which fine wire is wedged in the form of spiral or circles spotted and welded at each point.

In the present invention I stamped the grid out of metal with a die, so that the thin metallic portions which correspond to the wires of the grids are always in their proper location and of their proper size. In the wire type of grid it is very easy for some of the wires to become out of position, and in addition such a wire device is extremely delicate to handle, but with my invention it is strong and rugged and does away with many annoyances developed by the wire type of grid wherein many s ot welds are necessary where the wire touc ms the supports. In my invention I am also able to leave an openside to the grid, whereby the filament may be put directly in its place without the necessity of pulling it through a cylinder.

The entire construction of the tube duplicates in action the wire type of'grid, but does away with its many weak points and allows for extreme speed in assembly and production of control electrodes. In addition I have found that, due to the repelling of the electrons from each leg of a V-shape filament, the support should be between the two legs of the filaments, where the electron density is low due to the repelling of the negative particles. I have, therefore, by means of my invention been able to place the supporting member of the grid in the portion of the electron field of the least density, thus offering to the electron streams a lesser degree of obstruction than obtained by the standard type grid where the support of the grid is placed in the portion of the field of greatest density.

In the accompanying drawing I have shown certain specific embodiments of my invention, but it will be understood that the invention can be otherwise embodied and that the drawin is not to be construed as defining or limiting the scope of the invention, the claims appended to the specification being relied upon for that purpose.

Referring to the figures of the drawing:

Fig. 1 is a perspective view of a radio vacuum tube comprising my invention, certain parts being broken away to more clearly illustrate the invention.

Fig. 2 is a cross sectional View through Fig. 1.

Fig. 8 is a fragmentary detail View showing another form of control electrode.

Fig. 4 is a cross sectional view through Fig. 3.

Fig. 5 is a view similar to Fig. 2, but showing a modification thereof.

In the drawing, 1 indicates the bulb and 2 the base of a radio Vacuum tube. Mounted on the supporting base 3 within the tube are two plates 4, a control electrode 5 and a filament 6. The filament is supported by a wire 7 and, as illustrated, all of these parts are supported on the base 3.

The particular novelty of my present invention resides in the construction of the control electrode 5. As illustrated in Figs. 1 and 2, this member comprises a pair of plates secured together by rivets or other-v wise. These plates are each formed by die stamping in a manner to form a plurality of laterally extending arms 8 along the two opposite long edges of each plate. When two of these plates are assembled in the manner illustrated in Figs. 1 and 2, the arms 8 of the two plates extend outwardly in relatively angular directions in a manner forming a trough-like opening therebetween. The filament 6 is adapted to be received directly within this trough as illustrated in F i s. 1 and 2.

Fly improved control electrode or grid can be made in any of various forms. In Figs. 1 and 2 of the drawing, just described, the grid is of a double plate type. The Same can also be made of a single plate as in Figs. 3 and 4, if desired. In this construction the edges of the plate 9 are serrated and upset to form a plurality of outwardly extending arms 10. The alternate arms are bent in opposite directions in a manner to form a trough-like opening extending therebetween along the plate edges.

Normally, the plates 4 are mounted on opposite sides of the grid as shown in Fig. 2. If desired, however, these plates can be constructed in a manner to entirely surround the grid as illustrated in Fig. 5. In such construction the plates can be supported on posts 11 at opposite ends thereof.

As has been heretofore outlined, my improved grid construction has various advantages in manufacture, assembling and in operation. In manufacturing the grid, only a simple and inexpensive stamping operation is necessary. This operation can be done very cheaply by automatic machinery and the plates will all be exactly identical in construction and of an extremely rug ed character. Such a grid is of considerable advantage over the delicate grids now in common use.

In assembling, the grid is mounted on the base 3 and the arms 8 or 10 are open ready to receive the filament 6. This filament can be directly assembled in place laterally without the usual difliculty of drawing the filament through the cylinder, as is necessary in assembling the tubes now known.

It will furthermore be noted that the grid is supported on a post 12 between the two legs of the V-shape filament. As illustrated, in Figs. 2 and 5, the electron density is lowest ai; this supporting position. This placing of the grid support in the portion of the electron field of least density, offers to the electron streams a lesser degree of obstructlon than is obtained by the standard type grid where the support of the rid is placed in the portion of the fiel of greatest density.

It is believed that this and the further advantages of my invention will be clear without further description herein.

Having thus described my invention, what I claim and desire to secure by Letters Patcut is:

1. In a vacuum tube the combination of a base support, a control electrode mounted thereon and comprising plate means having a plurality of arms extending outwardly from edge portions thereof in relatively angular directions in a manner forming a trough therebetween, a filament extending along in the trough, and means for supporting the filament in place in the trough.

2. In a vacuum tube the combination of a base support, a control electrode mounted thereon and comprising plate means having a. plurality of arms extending outwardly from opposite edges thereof in relatively angular directions in a manner forming a trough between the arms along each of the said opposite edges, a filament extending along in the troughs, and means for supporting the filament in place in the troughs.

3. In a vacuum tube the combination of a base support, a control electrode mounted thereon and comprising plate means having the opposite edges thereof serrated and upset to form a filament-receiving opening extending along each of such edges, a filament extending along in such openings, means for supporting a filament in place in the openings, and means secured to the plate means between the said edges and supporting the same in the tube.

4. A control electrode comprising a plate member having two opposite edges thereof slotted to form a plurality of arms, certain of the said arms being bent in relatively opposite directions to form a trough along each edge of the plate member between the arms.

5. The process of forming a radio vacuum tube consisting of forming a control element by die stamping a metal plate member in a manner to form a plurality of relatively angular outwardly extending arms forming an extended trough-like opening therebetween, and assembling a filament directly therebetween laterally between the arms.

6. The process of forming a control electrode consisting of die stamping a metal plate member in a manner to form a plurality of relatively angular outwardly extending arms on the opposite edges thereof in amanner forming an extended troughlike opening between the arms along each said edge.

HERBERT E. METCALF. 

